Process for producing optically active succinimide derivatives and intermediates thereof

ABSTRACT

Provided is a process for producing (3R)-2′-(4-bromo-2-fluorobenzyl)spiro{pyrrolidine-3,4′(1′H)-pyrrolo[1,2-a]pyrazine}-1′,2,3′,5(2′H)-tetraone (compound A). The method includes converting an optically active succinimide derivative of formula (I) to compound A, in which the compound of formula (I) has been prepared by reacting a base with an optically active amide derivative of formula (VI).

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of copending U.S. patent application Ser. No. 13/148,263, now U.S. Pat. No. 8,633,001, filed on Aug. 5, 2011, which is the U.S. national phase of International Patent Application No. PCT/JP2010/000695 filed on Feb. 5, 2010, which claims the benefit of Japanese Patent Application No. 2009-025599, filed on Feb. 6, 2009, each of which is incorporated by reference in its entirety herein.

INCORPORATION-BY-REFERENCE OF MATERIAL ELECTRONICALLY SUBMITTED

Incorporated by reference in its entirety herein is a computer-readable nucleotide/amino acid sequence listing submitted concurrently herewith and identified as follows: 26,041 bytes ASCII (Text) file named “715624SequenceListing.txt,” created Dec. 9, 2013.

TECHNICAL FIELD

The present inventions relates to a process for producing optically active succinimide derivatives as key intermediates of (3R)-2′-(4-bromo-2-fluorobenzyl)spiro{pyrrolidine-3,4′(1′H)-pyrrolo[1,2-a]pyrazine}-1′,2,3′,5(2′H)-tetraone (henceforth referred to as “compound A” in this specification) represented by the following formula, which is expected to be a therapeutic agent for diabetic complications.

The present invention also relates to an ester derivative, optically active carboxylic acid derivative, and optically active amide derivative, which are useful intermediates of the compound A mentioned above, as well as processes for producing thereof and a process for producing the compound A by using said derivatives.

BACKGROUND ART

Methods for dividing a racemate into optical isomers (optical resolution methods) include a method of using an enzyme, a method of reacting optical isomers for conversion into salts and dividing the salts, a method of preparing a diastereomer mixture by reactions with optical isomers and then purifying the mixture for separation, and the like. Among them, the method of using an enzyme does not require optical isomers, and accordingly the method is advantageous since the reaction can be performed at low cost, for example. However, said method also has a problem that it is generally difficult to regioselectively and stereoselectively hydrolyze a specific alkoxycarbonyl of a triester or the like having two or more alkoxycarbonyls in a single molecule.

As methods for producing an optically active carboxylic acid derivative by regioselective and stereoselective hydrolysis using an esterase, Patent document 1 and Non-patent documents 1 and 2 report methods of asymmetrically hydrolyzing an α-(lower alkyl)-α-(protected amino)malonate diester derivative by using a pig liver esterase to produce an optically active α-(lower alkyl)-α-(protected amino)malonate monoester derivative.

(In the formulas, R⁴ represents benzyloxycarbonyl, tert-butoxycarbonyl, or the like, and R⁵ represents a lower alkyl or the like.)

Patent document 2 describes a method for producing (R)-2-amino-2-ethoxycarbonylsuccinimide (henceforth referred to as compound B), which is a key intermediate of the compound A, by using an esterase.

Methods for preparing the compound A from the compound B are described in Patent document 3, Non-patent document 3, and the like, and a method of preparing 4-tert-butyl 1-ethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate by reacting diethyl 2-benzyloxycarbonylaminomalonate and tert-butyl 2-bromoacetate is described in Reference Example 1 of Patent document 4.

PRIOR ART REFERENCES Patent Documents

-   Patent document 1: Japanese Patent Unexamined Publication (Kokai)     No. 10-245369 -   Patent document 2: International Patent Publication WO2008/035735 -   Patent document 3: Japanese Patent Unexamined Publication No.     05-186472 -   Patent document 4: Japanese Patent Unexamined Publication No.     06-192222

Non-Patent Documents

-   Non-patent document 1: Tetrahedron Letters (Tetrahedron Lett.),     1998, 39 (31), 5571-5574 -   Non-patent document 2: Tetrahedron Lett., 2000, 41 (26), 5013-5016 -   Non-patent document 3: Journal of Medicinal Chemistry (J. Med.     Chem.), 1998, 41, pp. 4118-4129

SUMMARY OF THE INVENTION Object to be Achieved by the Invention

An object of the present invention is to provide a process for producing optically active succinimide derivatives as key intermediates of the compound A.

Another object of the present invention is to provide an ester derivative, an optically active carboxylic acid derivative, and an optically active amide derivative, which are useful intermediates of the compound A, as well as processes for producing thereof and a process for producing the compound A by using said derivatives.

Means for Achieving the Object

The present invention relates to the following (1) to (16).

(1) A process for producing an optically active succinimide derivative represented by the formula (I):

[in the formula (I), R³ represents a lower alkyl] or a salt thereof, which comprises the following steps (A) to (D), and further comprises the step (E), if necessary: (A) the step of reacting an aminomalonate derivative represented by the formula (II):

[in the formula (II), R¹ represents amino or an amino protected with a protective group, and two of R³ represent the same lower alkyls having the same meaning as that defined above] and a halogenated acetic acid ester derivative represented by the formula (III): [Formula 5] Y—CH₂CO₂R²  (III) [in the formula (III), R² represents a lower alkyl, and Y represents a halogen] in the presence of a base for conversion into an ester derivative represented by the formula (IV):

[in the formula (IV), each of R¹, R², and R³ has the same meaning as that defined above] or a salt thereof, (B) the step of allowing an enzyme to react on the ester derivative represented by the formula (IV) or a salt thereof to convert the ester into an optically active carboxylic acid derivative represented by the formula (V):

[in the formula (V), each of R¹, R², and R³ has the same meaning as that defined above] or a salt thereof, (C) the step of reacting the optically active carboxylic acid derivative represented by the formula (V) or a salt thereof with an ammonia source in the presence of a condensing agent, or reacting the optically active carboxylic acid derivative represented by the formula (V) or a salt thereof with an activating reagent and then reacting the resultant with an ammonia source for conversion into an optically active amide derivative represented by the formula (VI):

[in the formula (VI), each of R¹, R², and R³ has the same meaning as that defined above] or a salt thereof, (D) the step of allowing a base to react on the optically active amide derivative represented by the formula (VI) or a salt thereof for conversion into an optically active succinimide derivative represented by the formula (I) or (VII):

[in the formula (VII), R^(1A) represents an amino protected with a protective group, and R³ has the same meaning as that defined above] or a salt thereof, and (E) the step of eliminating the protective group on R^(1A) of the optically active succinimide derivative represented by the formula (VII) or a salt thereof for conversion into an optically active succinimide derivative represented by the aforementioned formula (I) or a salt thereof. (2) A process for producing an ester derivative represented by the formula (IV-A):

[in the formula (IV-A), each of R¹, R^(2A), and R³ has the same meaning as that defined above] or a salt thereof, which comprises the step of allowing a halogenated acetic acid ester derivative represented by the formula (III-A): [Formula 10] Y—CH₂CO₂R^(2A)  (III-A) [in the formula (III-A), R^(2A) represents a lower alkyl selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, neopentyl and hexyl, and Y has the same meaning as that defined above] to react on an aminomalonate derivative represented by the formula (II) in the presence of a base. (3) A process for producing an optically active carboxylic acid derivative represented by the formula (V) or a salt thereof, which comprises the step of allowing an enzyme to react on an ester derivative represented by the formula (IV) or a salt thereof. (4) The production process according to (1) or (3), wherein the enzyme is a pig liver esterase or a rabbit liver esterase. (5) A process for producing an optically active amide derivative represented by the formula (VI) or a salt thereof, which comprises the step of reacting an optically active carboxylic acid derivative represented by the formula (V) or a salt thereof with an activating reagent, and further reacting the resultant with an ammonia source. (6) A process for producing an optically active amide derivative represented by the formula (VI) or a salt thereof, which comprises the step of reacting an optically active carboxylic acid derivative represented by the formula (V) or a salt thereof with an ammonia source in the presence of a condensing agent. (7) A process for producing an optically active succinimide derivative represented by the formula (I) or the formula (VII) or a salt thereof, which comprises the step of allowing a base to react on an optically active amide derivative represented by the formula (VI) or a salt thereof. (8) The production process according to any one of (1) to (7), wherein R¹ and R^(1A) mentioned in (1), (4) or (7), or R¹ mentioned in any one of (2) to (6) is benzyloxycarbonylamino, R² mentioned in (1) or any one of (3) to (7), or R^(2A) mentioned in (2) is ethyl, and R³ mentioned in any one of (1) to (7) is ethyl. (9) An ester derivative represented by the formula (IV-A):

[in the formula (IV-A), R¹ represents amino or an amino protected with a protective group, R^(2A) represents a lower alkyl selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, neopentyl and hexyl, and two of R³ represent the same lower alkyls having the same meaning as that defined above] or a salt thereof. (10) An optically active carboxylic acid derivative represented by the formula (V):

[in the formula (V), R² represent a lower alkyl, and each of R¹ and R³ has the same meaning as that defined above] or a salt thereof. (11) An optically active amide derivative represented by the formula (VI):

[in the formula (VI), each of R¹, R², and R³ has the same meaning as that defined above] or a salt thereof. (12) The derivative according to (9), wherein R¹ is benzyloxycarbonylamino, and R^(2A) and R³ are ethyls. (13) The derivative or a salt thereof according to (10) or (11), wherein R¹ is benzyloxycarbonylamino, and R² and R³ are ethyls. (14) A process for producing the compound A, which comprises the step of producing an optically active succinimide derivative represented by the formula (I) {henceforth referred to as compound (I)} by the production process according to (1) or (7), and the step of converting the compound (I) obtained in the above step into the compound A. (15) A process for producing the compound A, which comprises the following steps (a) to (e): (a) the step of producing the compound (I) by the method according to (1), (7) or (8); (b) the step of reacting the compound (I) obtained in the step (a) with 2,5-dimethoxytetrahydrofuran in the presence of an acid (for example, acetic acid and the like); (c) the step of reacting the product obtained in the step (b) with a trichloroacetylating reagent (for example, trichloroacetyl chloride, trichloroacetyl bromide, trichloroacetic anhydride, and the like); (d) the step of reacting the product obtained in the step (c) with 4-bromo-2-fluorobenzylamine; and (e) the step of isolating the compound A obtained in the step (d). (16) The production process according to (14) or (15), wherein R³ is ethyl.

Effect of the Invention

By using the intermediates and the production processes thereof according to the present invention, the compound (I) useful as an intermediate of the compound A and the compound A can be efficiently synthesized. In particular, the compound (I) and the compound A of high optical purity can be produced at a high yield according to the processes of the present invention, and therefore, they are advantageous from an industrial viewpoint and the like

MODES FOR CARRYING OUT THE INVENTION

It is defined above that the compound represented by the formula (I) is referred to as the compound (I), and such designation scheme is henceforth also applied to the compounds of the other formula numbers.

In the definitions of the groups included in the formulas (I) to (VII), (III-A), and (IV-A):

examples of the lower alkyl include, for example, a linear or branched alkyl having 1 to 6 carbon atoms, more specifically, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl, and the like. The halogen means an atom of fluorine, chlorine, bromine, or iodine.

Examples of the protective group of the “amino protected with a protective group” include, for example, protective groups for amino usually used in the organic synthesis chemistry [for example, those described in T. W. Greene, Protective Groups in Organic Synthesis, third edition, John Wiley & Sons Inc. (1999), and the like], and more preferred examples include such protective groups that can be deprotected by an action of a thiol or an acid, hydrogenolysis, or the like.

Examples of the protective group that can be deprotected by an action of a thiol include, for example, 2-nitrobenzenesulfonyl, 4-nitrobenzenesulfonyl, 2,4-dinitrobenzenesulfonyl, and the like.

Examples of the protective group that can be deprotected by an action of an acid include, for example, acetyl, trityl, tert-butoxycarbonyl, and the like, and more preferred examples include tert-butoxycarbonyl.

Examples of the protective group that can be deprotected by hydrogenolysis include, for example, benzyloxycarbonyl, benzyl and the like, which may have 1 to 3 substituents selected from the group consisting of a halogen atom, lower alkyl, lower alkoxyl and nitro on the benzene ring. More preferred examples include benzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, 4-chlorobenzyloxycarbonyl, 4-methylbenzyloxycarbonyl, 2-methoxybenzyloxycarbonyl, benzyl, 4-nitrobenzyl, 4-chlorobenzyl, 4-methylbenzyl, 2-methoxybenzyl, 4-methoxybenzyl, and the like.

In the present invention, the amino protected with a protective group may be converted into amino during the reaction.

Examples of R¹ and R^(1A) in the formulas include, for example, an amino protected with a protective group that can be deprotected by an action of a thiol or an acid, or hydrogenolysis, and the like, and preferred examples include benzyloxycarbonylamino and tert-butoxycarbonylamino.

Examples of R² and R³ in the formulas include, for example, ethyl, and the like. Examples of R^(2A) also include, for example, ethyl, and the like.

Examples of preferred combination of R¹, R² and R³ include, for example, such a combination that R¹ is benzyloxycarbonylamino, and R² and R³ are ethyls. Examples of preferred combination of R¹, R^(2A) and R³ include, for example, such a combination that R¹ is benzyloxycarbonylamino, and R^(2A) and R³ are ethyls. Examples of preferred combination of R^(1A) and R³ include, for example, such a combination that R^(1A) is benzyloxycarbonylamino and R³ is ethyl.

Examples of Y include a halogen, and preferred examples include iodine, bromine, chlorine, and the like. More preferred examples include bromine and chlorine.

Examples of the ammonia source include ammonia, an ammonia equivalent, and the like, and preferred examples include ammonia. Examples of the form of ammonia include gas or aqueous solution, and preferred examples include aqueous solution.

Examples of the ammonia equivalent include, for example, a salt of ammonia and an acid, preferred examples include ammonium acetate, ammonium formate, and ammonium carbonate, and more preferred examples include ammonium acetate.

Examples of the condensing agent include, for example, dicyclohexylcarbodiimide (DCC), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N,N′-carbonyldiimidazole (CDI), N-hydroxybenzotriazole (HOBT), diphenylphosphoric acid azide (DPPA), N-hydroxysuccinimide, N-hydroxyphthalimide, benzotriazol-1-yloxytrisdimethylaminophosphonium hexafluorophosphate (BOP), 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM), O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HBTU), 2-chloro-1-methylpyridinium iodide, and the like.

Examples of the activating reagent include, for example methyl chloroformate, ethyl chloroformate, isopropyl chloroformate, isobutyl chloroformate, pivaloyl chloride, phosgene, triphosgene, phosphorus oxychloride, phosphorus pentachloride, thionyl chloride, and the like, and preferred examples include isobutyl chloroformate.

Examples of the salt of the compound (I), (IV), (V), (VI), (VII) or (IV-A) include, for example, an acid addition salt, metal salt, ammonium salt, organic amine addition salt, amino acid addition salt, and the like. Examples of the acid addition salt include, for example, an inorganic acid salt such as hydrochloride, hydrobromide, nitrate, sulfate, and phosphate, organic acid salt such as acetate, oxalate, maleate, fumarate, citrate, benzoate and methanesulfonate, and the like. Examples of the metal salt include, for example, an alkali metal salt such as sodium salt and potassium salt, alkaline earth metal salt such as magnesium salt and calcium salt, aluminum salt, zinc salt, and the like. Examples of the ammonium salt include, for example, salts of ammonium, tetramethylammonium, and the like, and examples of the organic amine addition salt include addition salts of morpholine, piperidine, and the like. Examples of the amino acid addition salt include, for example, addition salts of lysine, glycine, phenylalanine, aspartic acid, glutamic acid, and the like.

The production processes of the present invention will be explained below. However, the reaction conditions such as reaction temperatures, types of reagents, amounts of reagents and reaction times are mentioned merely for exemplification, and they should not be construed any limitative way.

(In the formulas, R¹ represents amino or an amino protected with a protective group, R^(1A) represents an amino protected with a protective group, R² and R³ are the same or different, and represent a lower alkyl, and Y represents halogen.) (Step 1)

By reacting one equivalent to a large excess amount of the compound (III) with the compound (II) in a solvent at a temperature of −50 to 150° C. for 5 minutes to 72 hours in the presence of 1 to 30 equivalents of a base, the compound (IV) can be obtained. The reaction may be performed with addition of an alkali halide.

As the solvent, any solvent that does not participate in the reaction may be used. Examples include cyclohexane, benzene, toluene, xylene, diethyl ether, diisopropyl ether, tert-butyl methyl ether, tetrahydrofuran (THF), dioxane, pyridine, methanol, ethanol, isopropyl alcohol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetonitrile, and the like, and preferred examples include DMF. These can be used independently or as a mixture.

Examples of the base include an organic base and an inorganic base, preferred examples include an inorganic base, more preferred examples include sodium hydride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, cesium carbonate, sodium methoxide, sodium ethoxide, potassium tert-butoxide, and the like, still more preferred examples include sodium hydride, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, cesium carbonate, and the like, and most preferred examples include sodium hydride and potassium carbonate.

Examples of the alkali halide include an alkali bromide, an alkali iodide, and the like, preferred examples include an alkali iodide, and more preferred examples include lithium iodide, sodium iodide, potassium iodide, and cesium iodide. Most preferred examples include potassium iodide.

Examples of the compound (III) include ethyl 2-chloroacetate, ethyl 2-bromoacetate, and the like.

The compound (II) and the compound (III) can also be obtained as marketed products.

(Step 2)

By allowing an enzyme in an amount of 1/100,000 to 10-fold, preferably 1/10,000 to 1-fold, based on the substrate to react on the compound (IV) in water or a mixed solvent of water and a solvent at a substrate concentration of 0.1 to 50%, preferably 1 to 30%, a temperature of 0 to 60° C., preferably 10 to 40° C., and a reaction pH of 3 to 10, preferably 4 to 9, to allow the reaction for 1 to 200 hours, preferably 5 to 150 hours, the compound (V) can be obtained. The reaction can also be performed with adding a buffer or a metal salt.

Examples of the solvent include cyclohexane, benzene, toluene, xylene, diethyl ether, diisopropyl ether, tert-butyl methyl ether, THF, dioxane, methyl acetate, ethyl acetate, butyl acetate, methyl isobutyl ketone, acetone, dichloromethane, chloroform, dichloroethane, carbon tetrachloride, methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, DMF, DMSO, acetonitrile, and the like, and preferred examples include ethanol and acetonitrile. When a mixed solvent is used, the solvent may form a homogeneous system or a heterogeneous system of water and a solvent, and the solvent preferably forms such a homogeneous system.

Examples of the enzyme include an esterase derived from an animal, preferably derived from an organ of an animal. Examples of the animal include pig, rabbit, bovine, equine, canine, and bird, and pig and rabbit are more preferred. Examples of the organ as the origin of the esterase include liver, pancreas, small intestine, stomach, and the like, and liver and pancreas are preferred. Preferred examples of the esterase include, for example, pig liver esterase, rabbit liver esterase, and the like.

Examples of such an esterase include, a protein consisting of the amino acid sequence shown in SEQ ID NO: 2 or 4, or a protein consisting of an amino acid sequence having 95% or more, preferably 97% or more, more preferably 99% or more identity to the amino acid sequence shown in SEQ ID NO: 2 or 4, and having an esterase activity similar to that of the aforementioned protein, and the like. Examples also include a protein encoded by a DNA consisting of the nucleotide sequence shown in SEQ ID NO: 1 or 3, or a protein encoded by a DNA consisting of a nucleotide sequence having 95% or more, preferably 97% or more, more preferably 99% or more identity to the nucleotide sequence shown in SEQ ID NO: 1 or 3, and having an esterase activity similar to that of the aforementioned protein, and the like.

The aforementioned enzyme may be an enzyme extracted from an organ of an animal, or an enzyme produced by using a recombinant DNA technique.

The aforementioned enzyme may be a purified enzyme or a crude enzyme. Further, the enzyme may also be an immobilized enzyme obtained by immobilizing such an enzyme as mentioned above on a carrier by an appropriate means. The carrier may be any carrier generally used. Examples include, for example, polysaccharides such as cellulose, agarose, dextran, κ-carrageenan, alginic acid, gelatin and cellulose acetate; natural polymers such as gluten; inorganic substances such as activated carbon, glass, white clay, kaolinite, alumina, silica gel, bentonite, hydroxyapatite and calcium phosphate; synthetic adsorbent materials such as polyacrylamide, polyvinyl acetate, polypropylene glycol and urethane, and the like. As the immobilization method, for example, the cross-linking method, physical adsorption method and entrapment can be used.

Examples of the buffer include phosphate buffer, acetate buffer, citrate buffer, borate buffer, Tris buffer, and the like, and preferred examples include phosphate buffer. Concentration of the buffer is 0.1 mmol/L to 1 mol/L, preferably 1 mmol/L to 100 mmol/L.

Examples of the metal salt include NaCl, FeCl₃, KCl, CaCl₂, MgSO₄, MnSO₄, ZnCl₂, CoCl₂, and the like. Concentration of the metal salt is preferably 0.01 to 10%.

The optically active carboxylic acid derivative of the formula (V) obtained by the aforementioned reaction can be separated by, after completion of the reaction, filtering the reaction mixture to remove insoluble matter, adding an acid to adjust the filtrate to pH 1 to 3, preferably about pH 2, and then extracting the reaction product with an appropriate solvent.

(Step 3)

(A) By reacting one equivalent to a large excess amount of a condensing agent with the compound (V) in a solvent at a temperature of −50 to 150° C., preferably −30 to 80° C., for 5 minutes to 72 hours, then adding 1 equivalent to a large excess amount of an ammonia source and allowing to react at a temperature of −50 to 150° C., preferably −30 to 80° C., for 5 minutes to 72 hours, (B) by reacting one equivalent to a large excess amount of an activating reagent with the compound (V) in a solvent at a temperature of −50 to 150° C., preferably −30 to 80° C., for 5 minutes to 72 hours, then adding one equivalent to a large excess amount of an ammonia source and allowing to react at a temperature of −50 to 150° C., preferably −30 to 80° C., for 5 minutes to 72 hours, or (C) by adding one equivalent to a large excess amount of an ammonia source to the compound (V) in a solvent at a temperature of −50 to 150° C., preferably 20 to 80° C., in the presence of 1 equivalent to a large excess amount of a condensing agent and allowing to react for 5 minutes to 72 hours, the compound (VI) can be obtained.

For all the cases of (A) to (C), any solvent that does not participate in the reaction may be used. Examples include, for example, cyclohexane, benzene, toluene, xylene, diethyl ether, diisopropyl ether, tert-butyl methyl ether, THF, dioxane, methyl acetate, ethyl acetate, butyl acetate, methyl isobutyl ketone, acetone, pyridine, DMF, DMSO, dichloromethane, chloroform, acetonitrile, and the like, and preferred examples include THF. These solvents can be used independently or as an arbitrary mixture.

For all the cases of (A) to (C), at the time of the reaction with the ammonia source, such a solvent as water, methanol, ethanol and isopropyl alcohol may be used, in addition to the aforementioned solvent, and these solvents may be used independently or as an arbitrary mixture.

For all the cases of (A) to (C), the reaction may also be performed by adding 1/10 to 30 equivalents of a base.

Examples of the base include an organic base and an inorganic base, and preferred examples include an organic base. Examples of the organic base include, for example 1,8-diazabicyclo[5,4,0]-7-undecene (DBU), triethylamine, 4-dimethylaminopyridine, N,N-dimethylaniline, pyridine, N-methylmorpholine, ethyldiisopropylamine, and the like, and preferred examples include triethylamine. Examples of the inorganic base include, for example, sodium hydride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, cesium carbonate, sodium methoxide, sodium ethoxide, potassium tert-butoxide, and the like. As the condensing agent, those condensing agents mentioned above can be similarly used. Also as the activation reagent and the ammonia source, those mentioned above can be similarly used.

(Step 4)

By allowing one equivalent to a large excess amount of a base to react on the compound (VI) in a solvent at a temperature of −50 to 150° C., preferably −20 to 60° C., for 5 minutes to 72 hours, the compound (I) or the compound (VII) can be obtained.

Examples of the solvent include cyclohexane, benzene, toluene, xylene, pyridine, diethyl ether, diisopropyl ether, tert-butyl methyl ether, THF, dioxane, water, isopropyl alcohol, methanol, ethanol, DMF, DMSO, and the like, and preferred examples include ethanol. These solvents can be used independently or as an arbitrary mixture.

Examples of the base include sodium hydride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, cesium carbonate, sodium methoxide, sodium ethoxide, potassium tert-butoxide, and the like, and preferred examples include sodium ethoxide.

(Step 5)

When R^(1A) of the compound (VII) is an amino protected with a protective group that can be deprotected by hydrogenolysis, by adding a metal catalyst in an amount of 1/10 to 50% by weight, preferably 1 to 10% by weight, of the substrate in a solvent, and allowing to react at a temperature of −50 to 150° C., preferably 20 to 100° C., under a pressure of 1 to 10 atmospheres, preferably 1 to 5 atmospheres, for 5 minutes to 72 hours in the presence of hydrogen or a hydrogen donor, the compound (I) can be obtained.

Examples of the solvent include acetic acid, methyl acetate, ethyl acetate, butyl acetate, diethyl ether, diisopropyl ether, tert-butyl methyl ether, THF, dioxane, water, methanol, ethanol, isopropyl alcohol, DMF, and the like, and preferred examples include ethanol. These solvents can be used independently or as an arbitrary mixture.

Examples of the metal catalyst include platinum(IV) oxide, platinum/carbon, palladium(II) hydroxide, palladium(II) hydroxide/carbon, palladium/carbon, palladium/alumina, ruthenium/carbon, rhodium/carbon, rhodium/alumina, Wilkinson catalyst, Raney nickel, and the like, and preferred examples include palladium/carbon. Although palladium content in palladium/carbon is not particularly limited, it is preferably, for example, 5 to 10%.

Examples of the hydrogen donor include ammonium formate, cyclohexene, cyclohexa-1,3-diene, cyclohexa-1,4-diene, and the like.

When R^(1A) of the compound (VII) is an amino protected with a protective group that can be deprotected by an action of an acid, by allowing an acid to react on the protective group without solvent or in a solvent at a temperature of −50 to 150° C., preferably 20 to 100° C., the compound (I) can be obtained.

Examples of the solvent include cyclohexane, benzene, toluene, xylene, diethyl ether, diisopropyl ether, tert-butyl methyl ether, THF, dioxane, methyl acetate, ethyl acetate, butyl acetate, water, isopropyl alcohol, methanol, ethanol, DMF, dichloromethane, chloroform, and the like, and these solvent can be used independently or as an arbitrary mixture.

Examples of the acid include an inorganic acid, an organic acid, and the like, examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, and the like, and examples of the organic acid include acetic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, p-toluenesulfonic acid, and the like. Preferred examples include trifluoroacetic acid.

When R^(1A) of the compound (VII) is an amino protected with a protective group that can be deprotected by an action of a thiol, by allowing one equivalent to a large excess amount of a thiol to react on the protective group in a solvent at a temperature of −50 to 150° C., preferably 20 to 100° C., for 5 minutes to 72 hours in the presence of 1 equivalent to a large excess amount of a base, the compound (I) can be obtained.

Examples of the solvent include cyclohexane, benzene, toluene, xylene, pyridine, diethyl ether, THF, dioxane, methyl acetate, ethyl acetate, butyl acetate, water, acetone, isopropyl alcohol, methanol, ethanol, DMF, dichloromethane, chloroform, and the like, and these solvent can be used independently or as an arbitrary mixture.

As the thiol, any compound having sulfhydryl group can be used. Preferred examples include a thiophenol which may have a substituent and a lower alkyl thiol which may have a substituent, and more preferred examples include thiophenol, methanethiol, ethanethiol, 1-dodecanethiol, and the like.

Examples of the base include an organic base and an inorganic base. Examples of the organic base include, for example, DBU, triethylamine, 4-dimethylaminopyridine, N,N-dimethylaniline, pyridine, N-methylmorpholine, ethyldiisopropylamine, and the like, and examples of the inorganic base include, for example, sodium hydride, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium carbonate, potassium hydrogencarbonate, sodium methoxide, sodium ethoxide, potassium tert-butoxide, and the like, and preferred examples include potassium carbonate and triethylamine.

It is described in Non-patent document 3 that the compound (I) and the compound B:

can be used as intermediates of the compound A, and accordingly, it is obvious to those skilled in the art that the compound (I) and the compound B can be used as raw materials for the production of compound A. According to the descriptions of the above literature, for example, each of the steps (b) to (e) of (15) mentioned above are performed as follows.

In the step (b), for example, a mixture of the compound B, about 1.5 equivalent of 2,5-dimethoxytetrahydrofuran and an excess amount of acetic acid is stirred at about 70° C. for about 1.5 hours. In a usual case, a crude reaction product can be isolated in a conventional manner, and this product can be used for the following step.

In the step (c), for example, a mixture of the product obtained in the aforementioned step (b), about 3 equivalents of trichloroacetyl chloride and an appropriate amount of chloroform is refluxed by heating for about 16 hours. Instead of chloroform, another inert solvent (for example, dichloromethane, THF, and the like) can also be used. In a usual case, a crude reaction product can be isolated in a conventional manner, and this product can be used for the following step.

In the step (d), for example, the product obtained in the aforementioned step (c), about 1.2 equivalents of 4-bromo-2-fluorobenzylamine hydrochloride, and about 2.5 equivalents of triethylamine are stirred at room temperature for about 16 hours in an appropriate amount of dry DMF solvent. In a usual case, a crude reaction product (the compound A) can be isolated in a conventional manner, and this product can be used for the following step.

In the step (e), for example, the compound A obtained in the step (d) is recrystallized from an appropriate amount of a mixed solvent of ethyl acetate and hexane. As other recrystallization solvents, alcohols such as ethanol can also be used.

EXAMPLES

Hereafter, the present invention will be more specifically explained with reference to examples and reference examples. However, the present invention is not limited to these examples.

The proton nuclear magnetic resonance (¹H NMR) spectra mentioned in the examples and the reference examples were measured at 300 MHz, and depending on the type of compound and measurement conditions, exchangeable proton may not be clearly observed. As indications of the multiplicity of signals, those usually used are applied, and “br” indicates a signal having an apparently large width. Furthermore, molecular weights of the compounds were confirmed by mass spectrometry (MS).

As for the conversion reaction from diethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate to (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate, content analysis was performed, and production amount was obtained as volume×content, and used to calculate the yield. The content analysis was performed by HPLC under the following conditions. More specifically, the column was Inertsil ODS-3 (φ4.6×75 mm, 3 μm) produced by GL Sciences Inc., the developing solvent was acetonitrile/0.05 mol/L phosphate buffer (pH 2.5)=50/50 (volume ratio), the flow rate was 1.0 mL/minute, the oven temperature was 40° C., and the detection wavelength was 254 nm. The content was determined by using a calibration curve prepared with standard solutions of known concentrations.

The optical purity analysis was performed by HPLC under the following conditions. As the column, CHIRALCEL OJ-RH (φ4.6×150 mm) produced by Daicel Chemical Industries, Ltd. was used. The optical purity analysis of 1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate was performed with acetonitrile/aqueous perchloric acid (pH 2.0)=30/70 (volume ratio) as the developing solvent at a flow rate of 1.0 mL/minute, oven temperature of 20° C., and detection wavelength of 254 nm. The optical purity analysis of diethyl 2-benzyloxycarbonylamino-2-carbamoylsuccinate was performed with acetonitrile/water=30/70 (volume ratio) as the developing solvent at a flow rate of 0.5 mL/minute, oven temperature of 20° C., and detection wavelength of 254 nm. The optical purity analysis of 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinimide was performed with acetonitrile/aqueous perchloric acid (pH 2.0)=30/70 (volume ratio) as the developing solvent at a flow rate of 0.5 mL/minute, oven temperature of 20° C., and detection wavelength of 254 nm. The optical purity analysis of (R)-2-amino-2-ethoxycarbonylsuccinimide was performed with aqueous perchloric acid (pH 1.0) as the developing solvent at a flow rate of 0.45 mL/minute, oven temperature of 5° C., and detection wavelength of 196 nm.

The intermediates and the objective compounds in the aforementioned production processes can be isolated and purified with separation and purification methods usually used in the synthetic organic chemistry, for example, filtration, extraction, washing, drying, concentration, recrystallization, various chromatography techniques, and the like. The intermediates may also be used for the subsequent reactions without particular purification.

In case a salt of the compound (I), (IV), (V), (VI), (VII) or (IV-A) is desired to be obtained, when the compound (I), (IV), (V), (VI), (VII) or (IV-A) is obtained in the form of salt, the salt per se may be purified, and when the compound (I), (IV), (V), (VI), (VII) or (IV-A) is obtained in a free form, the compound can be dissolved or suspended in an appropriate solvent, an acid or a base can be added to the solution or suspension, and a resulted salt can be separated and purified.

The compound (I), (IV), (V), (VI), (VII) or (IV-A), and a salt thereof may exist in the form of adduct with water or various solvents, and such adducts also fall within the scope of the present invention.

Example 1 Production of diethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate (Ethyl Chloroacetate Method)

A suspension of diethyl 2-benzyloxycarbonylaminomalonate (5.0 g), potassium carbonate (2.7 g), potassium iodide (0.27 g), and ethyl 2-chloroacetate (2.6 g) in DMF (50 mL) was stirred at 50° C. for 1 hour. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was crystallized from ethyl acetate/n-hexane to obtain the title compound (5.5 g, yield: 86%) as colorless crystals.

¹H NMR (CDCl₃) δ (ppm): 7.34 (5H, m), 6.39 (1H, s), 5.10 (2H, s), 4.24 (4H, q, J=6.9 Hz), 4.10 (2H, q, J=7.2 Hz), 3.49 (2H, s), 1.21 (9H, m)

MS (FAB): m/z 396 (M+H⁺)

HR-MS (FAB): calcd for C₁₉H₂₆NO₈ 396.1658. found 396.1653 (M+H⁺).

Example 2 Production of diethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate (Ethyl Bromoacetate Method)

A solution of diethyl 2-benzyloxycarbonylaminomalonate (50 g) in anhydrous DMF (300 mL) was added portionwise with sodium hydride (60%, 6.47 g) with ice cooling and stirring, then the mixture was stirred at room temperature for 30 minutes, and subsequently added with ethyl 2-bromoacetate (22.6 g), and the mixture was stirred overnight. The reaction mixture was poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (5:1) for purification, and then crystallized from ethyl acetate/n-hexane to obtain the title compound (46.7 g, yield: 83%) as colorless crystals.

Example 3 Production of (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate (Hydrolysis with Pig Liver Esterase)

4.0 g of pig liver esterase produced by Sigma [PLE (27 kU/g), lyophilized product, product number: E3019] was dissolved in a 0.05 mol/L phosphate buffer adjusted to pH 6.5 (360 mL), and the solution was added with a solution of diethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate (4.0 g) dissolved in ethanol (40 mL). The mixture was stirred at 30° C. for 20 hours to obtain (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate at a yield of 84% and optical purity of 93.6% ee.

After completion of the reaction, the reaction mixture was filtered by using a filtration aid (KC Floc 100) to remove the insoluble matter. The filtrate was cooled, and adjusted to pH 2 by adding 6 mol/L hydrochloric acid, then the objective substance was extracted with ethyl acetate, and the extract was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with chloroform/methanol (10:1) for purification, to obtain the title compound (3.26 g, yield: 80%). Optical rotation [α]_(D) ₂₈ was −0.6° (c 0.58, ethanol), and optical purity was 93.6% ee.

¹H NMR (CDCl₃) δ (ppm): 7.35 (5H, m), 6.51 (1H, s), 5.09 (2H, m), 4.24 (2H, q, J=7.2 Hz), 4.08 (2H, q, J=7.2 Hz), 3.48 (2H, s), 1.19 (6H, m)

MS (FAB): m/z 368 (M+H⁺)

HR-MS (FAB): calcd for C₁₇H₂₂NO₈ 368.1345. found 368.1314 (M+H⁺).

Example 4 Production of (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate (Hydrolysis with Rabbit Liver Esterase)

5 mg of rabbit liver esterase produced by Sigma (80 kU/g, lyophilized product, product number: E0887) was dissolved in a 0.05 mol/L phosphate buffer adjusted to pH 6.5 (0.4 mL), and the solution was added with a solution of diethyl 2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinate (5 mg) dissolved in ethanol (0.05 mL). The mixture was stirred at 30° C. for 16 hours to obtain (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate at a yield of 52% and optical purity of 94.6% ee.

Example 5 Production of (R)-diethyl 2-benzyloxycarbonylamino-2-carbamoylsuccinate

A solution of (R)-1-ethyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate (1.8 g) in THF (20 mL) was added with triethylamine (0.96 mL) and isobutyl chloroformate (0.84 mL, 0.87 g) in this order at −15° C. with stirring, and the mixture was stirred for 5 minutes. A solution of 25% aqueous ammonia (0.47 mL) was dropped into the reaction mixture at the same temperature. The reaction mixture was stirred at the same temperature for 1 hour, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (1:1) for purification, and then crystallized from ethyl acetate/n-hexane to obtain the title compound (1.51 g, yield: 84%) as colorless crystals. Optical rotation [α]_(D) ₂₅ was −5.7° (c 0.52, ethanol) and optical purity was 96.1% ee.

¹H NMR (CDCl₃) δ (ppm): 7.34 (5H, m), 6.51 (1H, br), 6.35 (1H, br), 5.63 (1H, br), 5.12 (2H, s), 4.26 (2H, m), 4.10 (2H, q, J=7.2 Hz), 3.48 (2H, s), 1.23 (6H, m)

MS (FAB): 367 (M+H⁺)

HR-MS (FAB): calcd for C₁₇H₂₃N₂O₇ 367.1505. found 367.1509 (M+H⁺).

Example 6 Production of (R)-2-benzyloxycarbonylamino-2-ethoxycarbonylsuccinimide

A solution of (R)-diethyl 2-benzyloxycarbonylamino-2-carbamoylsuccinate (200 mg) in dehydrated ethanol (10 mL) was added with sodium ethoxide (41 mg) with ice cooling and stirring, the mixture was stirred at the same temperature for 2 hours, then cold 1 mol/L hydrochloric acid was poured into the mixture, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was recrystallized from ethyl acetate/n-hexane to obtain the title compound (149 mg, yield: 85%) as colorless crystals. Optical rotation [α]_(D) ₂₈ was −31.8° (c 0.59, ethanol), and optical purity was 99.2% ee.

¹H NMR (CDCl₃) δ (ppm): 8.39 (1H, s), 7.36 (5H, m), 6.27 (1H, s), 5.12 (2H, m), 4.32 (2H, q, J=6.9 Hz), 3.18 (2H, m), 1.29 (3H, t, J=7.1 Hz)

MS (FAB): 321 (M+H⁺)

HR-MS (FAB): calcd for C₁₅H₁₇N₂O₆ 321.1087. found 321.1074 (M+H⁺).

Example 7 Production of (R)-2-amino-2-ethoxycarbonylsuccinimide

(R)-2-Benzyloxycarbonylamino-2-ethoxycarbonylsuccinimide (80 mg) was dissolved in ethanol (10 mL), the solution was added with 5% palladium/carbon (4 mg), and catalytic hydrogenation was performed at room temperature under a hydrogen atmosphere. After the catalyst was removed by filtration, the filtrate was concentrated under reduced pressure. The residue was recrystallized from ethanol to obtain the title compound (43 mg, yield: 93%) as colorless crystals. Optical rotation [α]_(D) ₂₄ was −35.9° (c 0.22, ethanol). Optical purity was more than 99.9% ee.

¹H NMR (CDCl₃) δ (ppm): 4.28 (2H, q, J=7.2 Hz), 3.19 (1H, d, J=18.0 Hz), 2.74 (1H, d, J=18.0 Hz), 1.30 (3H, t, J=7.1 Hz)

MS (FAB): 187 (M+H⁺)

HR-MS (FAB): calcd for C₇H₁₁N₂O₄ 187.0719. found 187.0700 (M+H⁺).

Example 8

The following compounds 1 to 4 were synthesized in the same manner as that of Example 2.

Production of Compound 1, diethyl 2-benzyloxycarbonylamino-2-(methoxycarbonylmethyl)malonate

A suspension of diethyl 2-benzyloxycarbonylaminomalonate (3.0 g), potassium carbonate (1.6 g), potassium iodide (0.19 g), and methyl 2-bromoacetate (1.9 g) in DMF (50 mL) was stirred at 50° C. for 1 hour. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (4:1) for purification, and then crystallized from ethyl acetate/n-hexane to obtain the title compound (3.52 g, yield: 95%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 7.34 (5H, m), 6.40 (1H, s), 5.09 (2H, s), 4.24 (4H, q, J=6.9 Hz), 3.64 (3H, s), 3.51 (2H, s), 1.22 (6H, m)

MS (FAB): m/z 382 (M+H⁺)

Production of Compound 2, diethyl 2-benzyloxycarbonylamino-2-(isopropyloxycarbonylmethyl)malonate

A suspension of diethyl 2-benzyloxycarbonylaminomalonate (5.0 g), potassium carbonate (2.7 g), potassium iodide (0.32 g), and isopropyl 2-bromoacetate (3.5 g) in DMF (50 mL) was stirred at 50° C. for 1 hour. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, and then purification was performed with n-hexane/ethyl acetate (5:1), to obtain the title compound (6.8 g, yield: 99%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 7.33 (5H, m), 6.38 (1H, s), 5.10 (2H, s), 4.96 (1H, m), 4.24 (4H, q, J=6.9 Hz), 3.45 (2H, s), 1.23 (6H, m), 1.18 (6H, d, J=6.3 Hz)

MS (FAB): m/z 410 (M+H⁺)

Production of Compound 3, diethyl 2-benzyloxycarbonylamino-2-(t-butoxycarbonylmethyl)malonate

A suspension of diethyl 2-benzyloxycarbonylaminomalonate (5.0 g), potassium carbonate (2.7 g), potassium iodide (0.27 g), and t-butyl 2-bromoacetate (4.1 g) in DMF (50 mL) was stirred at 50° C. for 1 hour. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, and then purification was performed with n-hexane/ethyl acetate (5:1), to obtain the title compound (6.9 g, yield: 99%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 7.34 (5H, m), 6.38 (1H, s), 5.10 (2H, s), 4.23 (4H, q, J=6.9 Hz), 3.40 (2H, s), 1.39 (9H, s), 1.22 (6H, t, J=7.1 Hz)

MS (FAB): m/z 424 (M+H⁺)

Production of Compound 4, diethyl 2-benzyloxycarbonylamino-2-(benzyloxycarbonylmethyl)malonate

A solution of diethyl 2-benzyloxycarbonylaminomalonate (30 g) in anhydrous DMF (100 mL) was added portionwise with sodium hydride (60%, 4.27 g) with ice cooling and stirring, then the mixture was stirred at room temperature for 30 minutes, and then added with benzyl 2-bromoacetate (28.9 g), and the mixture was stirred overnight. The reaction mixture was poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, and then purification was performed with n-hexane/ethyl acetate (4:1), to obtain the title compound (43.9 g, yield: 99%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 7.33 (10H, m), 6.39 (1H, s), 5.09 (4H, s), 4.20 (4H, q, J=6.9 Hz), 3.56 (2H, s), 1.23 (6H, m)

MS (FAB): m/z 458 (M+H⁺)

Example 9 Compound 5: (R)-1-Methyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate

10 mg of pig liver esterase produced by Sigma [PLE (27 kU/g), lyophilized product, product number: E3019] was dissolved in a 0.1 mol/L phosphate buffer adjusted to pH 6.5 (0.9 mL), and the solution was added with a solution of the compound 1 (10 mg) dissolved in acetonitrile (0.1 mL). The mixture was stirred at 30° C. for 4 hours, and it was confirmed by HPLC that the compound 5 was obtained at a yield of 99.0%. The HPLC conditions were changed from those mentioned above, that is, methanol/water=60/40 (volume ratio, containing 0.1% trifluoroacetic acid) was used as the developing solvent, and the flow rate was 0.7 mL/minute. The product was confirmed by MS analysis. It was confirmed by HPLC (conditions were changed from those mentioned above, so that 40% acetonitrile was used as the developing solvent) that optical purity of the product was 93.1% ee.

MS (FAB): m/z 354 (M+H⁺)

Example 10

The compounds 2 to 4 were reacted in the same manner as that of Example 9 to obtain the corresponding compounds 6 to 8.

Compound 6: (R)-1-Isopropyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate Example 11 Compound 7: (R)-1-t-Butyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate Example 12 Compound 8: (R)-1-Benzyl hydrogen 3-benzyloxycarbonylamino-3-ethoxycarbonylsuccinate

Acetonitrile concentration of the developing solvent for the optical purity measurement was changed from the condition mentioned above, and the following conditions were used.

Example 10: 30% Acetonitrile

Example 11: 40% Acetonitrile

Example 12: 40% Acetonitrile

The results are summarized below.

TABLE 1 Optical Raw Yield purity MS (FAB): material Product % % ee m/z Example Compound 2 Compound 6 97.4 97.4 382 (M + H+) 10 Example Compound 3 Compound 7 98.5 97.9 396 (M + H⁺) 11 Example Compound 4 Compound 8 46.5 86.7 430 (M + H⁺) 12

Example 13 Production of diethyl 2-t-butyloxycarbonylamino-2-ethoxycarbonylsuccinate

A suspension of diethyl 2-t-butyloxycarbonylaminomalonate (5.0 g), potassium carbonate (3.0 g), and ethyl 2-bromoacetate (3.9 g) in DMF (20 mL) was stirred at 50° C. for 4 hours. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, and then purification was performed with n-hexane/ethyl acetate (5:1), to obtain the title compound (5.7 g, yield: 79%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 6.13 (1H, s), 4.25 (4H, m), 4.12 (2H, q, J=6.9 Hz), 3.45 (2H, s), 1.43 (9H, s), 1.26 (9H, m)

MS (FAB): m/z 362 (M+H⁺)

Example 14 Production of (R)-1-ethyl hydrogen 3-t-butyloxycarbonylamino-3-ethoxycarbonylsuccinate (Hydrolysis with Pig Liver Esterase)

1.0 g of pig liver esterase produced by Sigma [PLE (27 kU/g), lyophilized product, product number: E3019] was dissolved in a 0.1 mol/L phosphate buffer adjusted to pH 7.5 (90 mL), and the solution was added with a solution of diethyl 2-t-butyloxycarbonylamino-2-ethoxycarbonylsuccinate (1.0 g) dissolved in acetonitrile (10 mL). The mixture was stirred at 30° C. for 4 hours to allow the reaction. After completion of the reaction, the reaction mixture was filtered by using a filtration aid (KC Floc 100) to remove the insoluble matter. The filtrate was cooled, and adjusted to pH 2 by adding 6 mol/L hydrochloric acid, then the objective substance was extracted with ethyl acetate, and the extract was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to obtain the title compound (1.0 g).

MS (FAB): m/z 334 (M+H⁺)

Example 15 Production of (R)-diethyl 2-t-butyloxycarbonylamino-2-carbamoylsuccinate

A solution of (R)-1-ethyl hydrogen 3-t-butyloxycarbonylamino-3-ethoxycarbonylsuccinate (1.0 g) obtained in Example 14 in THF (20 mL) was added with triethylamine (0.62 mL) and isobutyl chloroformate (0.55 mL, 0.57 g) in this order at −15° C. with stirring, and the mixture was stirred for 30 minutes. A solution of 25% aqueous ammonia (0.30 mL) was dropped into the reaction mixture at the same temperature. The reaction mixture was stirred at the same temperature for 30 minutes, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and then the extract was dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (1:1) for purification, and then crystallized from ethyl acetate/n-hexane to obtain the title compound (0.67 g, yield: 73%) as colorless crystals. Optical rotation [α]_(D) ₂₂ was +2.74° (c 0.50, ethanol).

¹H NMR (CDCl₃) δ (ppm): 6.42 (1H, br), 6.23 (1H, br), 5.50 (1H, br), 4.27 (2H, m), 4.14 (2H, q, J=7.2 Hz), 3.43 (2H, s), 1.44 (9H, s), 1.26 (6H, m)

MS (FAB): m/z 333 (M+H⁺)

Example 16 Production of (R)-2-t-butyloxycarbonylamino-2-ethoxycarbonylsuccinimide

(R)-diethyl 2-t-butyloxycarbonylamino-2-carbamoylsuccinate (590 mg) obtained in Example 15 was dissolved in acetone (6 mL) and water (6 mL), the solution was added with potassium carbonate (295 mg), the mixture was stirred for 6 hours, 1 mol/L hydrochloric acid was poured to the mixture, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (1:1) for purification, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (450 mg, yield: 88%) as colorless crystals. Optical rotation [α]_(D) ₂₅ was −39.1° (c 0.50, ethanol).

¹H NMR (CDCl₃) δ (ppm): 8.50 (1H, br), 5.99 (1H, br), 4.32 (2H, q, J=7.2 Hz), 3.16 (2H, m), 1.44 (9H, s), 1.30 (3H, t, J=7.2 Hz)

MS (FAB): m/z 287 (M+H⁺)

Example 17 Production of (R)-2-amino-2-ethoxycarbonylsuccinimide hydrochloride

(R)-2-t-Butyloxycarbonylamino-2-ethoxycarbonylsuccinimide (380 mg) obtained in Example 16 was dissolved in a 4 mol/L solution of hydrochloric acid in ethyl acetate (8 mL), and the reaction mixture was stirred for 1 hour, and then concentrated under reduced pressure. The residue was suspended in ether and filtered to obtain the title compound (288 mg, yield: 97%) as white crystals. Optical rotation [α]_(D) ₂₅ was −14.8° (c 1.0, methanol). Optical purity was 75.6% ee.

¹H NMR (DMSO-d₆) δ (ppm): 12.36 (1H, br), 9.65 (2H, br), 4.27 (2H, q, J=7.2 Hz), 3.34 (1H, d, J=18.2 Hz), 3.11 (1H, d, J=18.2 Hz), 1.20 (3H, t, J=7.2 Hz)

MS (FAB): m/z 187 (M+H⁺)

Example 18 Production of diethyl 2-t-butyloxycarbonylamino-2-(benzyloxycarbonylmethyl)malonate

A suspension of diethyl 2-t-butyloxycarbonylaminomalonate (5.0 g), potassium carbonate (3.0 g), and benzyl 2-bromoacetate (5.4 g) in DMF (20 mL) was stirred at 50° C. for 4 hours. The reaction mixture was cooled, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and the extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, and then purification was performed with n-hexane/ethyl acetate (5:1), to obtain the title compound (6.5 g, yield: 85%) as colorless oil.

¹H NMR (CDCl₃) δ (ppm): 7.32 (5H, m), 6.1 (1H, s), 5.11 (2H, s), 4.21 (4H, m), 3.53 (2H, s), 1.41 (9H, s), 1.22 (6H, t, J=7.1 Hz)

MS (FAB): m/z 424 (M+H⁺)

Example 19 Production of (R)-1-benzyl hydrogen 3-t-butyloxycarbonylamino-3-ethoxycarbonylsuccinate (Hydrolysis with Pig Liver Esterase)

1.0 g of pig liver esterase produced by Sigma [PLE (27 kU/g), lyophilized product, product number: E3019] was dissolved in a 0.1 mol/L phosphate buffer adjusted to pH 7.5 (90 mL), and the solution was added with a solution of diethyl 2-t-butyloxycarbonylamino-2-(benzyloxycarbonylmethyl)malonate (1.0 g) dissolved in acetonitrile (10 mL). The mixture was stirred at 30° C. for 4 hours to produce the title compound. Optical purity measured by HPLC was 78.1% ee. After completion of the reaction, the reaction mixture was filtered by using a filtration aid (KC Floc 100) to remove the insoluble matter. The filtrate was cooled, and adjusted to pH 2 by adding 6 mol/L hydrochloric acid, then the objective substance was extracted with ethyl acetate, and the extract was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to obtain the title compound (1.0 g).

MS (FAB): m/z 396 (M+H⁺)

Example 20 Production of (R)-1-benzyl ethyl 3-t-butyloxycarbonylamino-3-carbamoylsuccinate

A solution of (R)-1-benzyl hydrogen 3-t-butyloxycarbonylamino-3-ethoxycarbonylsuccinate (1.0 g) obtained in Example 19 in THF (20 mL) was added with triethylamine (0.62 mL) and isobutyl chloroformate (0.55 mL, 0.57 g) in this order at −15° C. with stirring, and the mixture was stirred for 30 minutes. A solution of 25% aqueous ammonia (0.30 mL) was dropped into the reaction mixture at the same temperature. The reaction mixture was stirred at the same temperature for 30 minutes, and then poured into diluted hydrochloric acid, the mixture was extracted with ethyl acetate, and then the extract was dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (1:1) for purification, and then crystallized from ethyl acetate/n-hexane to obtain the title compound (0.60 g, yield: 55%) as colorless crystals. Optical rotation [α]_(D) ₂₅ was +1.28° (c 0.50, ethanol).

¹H NMR (CDCl₃) δ (ppm): 7.33 (5H, m), 6.39 (1H, br), 6.21 (1H, br), 5.56 (1H, br), 5.12 (2H, s), 4.22 (2H, q, J=7.2 Hz), 3.51 (2H, s), 1.41 (9H, s), 1.22 (3H, t, J=7.0 Hz)

MS (FAB): m/z 395 (M+H⁺)

Example 21 Production of (R)-2-t-butyloxycarbonylamino-2-ethoxycarbonylsuccinimide

(R)-1-Benzyl ethyl 3-t-butyloxycarbonylamino-3-carbamoylsuccinate (550 mg) obtained in Example 20 was dissolved in acetone (11 mL) and water (6 mL), the solution was added with potassium carbonate (231 mg), the mixture was stirred for 5 hours, and poured with 1 mol/L hydrochloric acid, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, and then dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure, and the residue was subjected to silica gel column chromatography, in which elution was performed with n-hexane/ethyl acetate (1:1) for purification, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (358 mg, yield: 90%) as colorless crystals. Optical rotation [α]_(D) ₂₅ was −29.5° (c 0.50, ethanol).

¹H NMR (CDCl₃) δ (ppm): 8.33 (1H, br), 5.99 (1H, br), 4.32 (2H, q, J=7.2 Hz), 3.16 (2H, m), 1.44 (9H, s), 1.30 (3H, t, J=7.2 Hz)

MS (FAB): m/z 287 (M+H⁺)

Example 22 Production of (R)-2-amino-2-ethoxycarbonylsuccinimide hydrochloride

(R)-2-t-Butyloxycarbonylamino-2-ethoxycarbonylsuccinimide (243 mg) obtained in Example 21 was dissolved in a 4 mol/L solution of hydrochloric acid in ethyl acetate (5 mL), and the reaction mixture was stirred for 1 hour, and then concentrated under reduced pressure. The residue was suspended in ether, and filtered to obtain the title compound (179 mg, yield: 95%) as white crystals. Optical rotation [α]_(D) ₂₅ was −14.2° (c 1.0, methanol). Optical purity was 71.6% ee.

¹H NMR (DMSO-d₆) δ (ppm): 12.36 (1H, br), 9.65 (2H, br), 4.27 (2H, q, J=7.2 Hz), 3.34 (1H, d, J=18.2 Hz), 3.11 (1H, d, J=18.2 Hz), 1.20 (3H, t, J=7.2 Hz)

MS (FAB): m/z 187 (M+H⁺)

INDUSTRIAL APPLICABILITY

According to the present invention, there are provided a process for producing optically active succinimide derivatives as key intermediates of the compound A, which is useful as a therapeutic agent for diabetic complications, as well as an ester derivative, an optically active carboxylic acid derivative, and an optically active amide derivative, which are useful intermediates of the compound A. There are also provided processes for producing these compounds and a process for producing the compound A by using the derivatives. 

What is claimed is:
 1. A process for producing compound A,

or a salt thereof, said process comprises: (A) reacting an ester derivative represented by formula (IV):

 or a salt thereof, [wherein in said formula (IV), R¹ is an amino or an amino protected with a protective group and R² and R³ are lower alkyls independently selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, and hexyl] with a pig liver esterase or a rabbit liver esterase for conversion of said ester derivative into an optically active carboxylic acid derivative represented by formula (V):

 or a salt thereof, [wherein in said formula (V), each of R¹, R², and R³ has the same meaning as defined above]; (B) reacting said optically active carboxylic acid derivative represented by formula (V) or said salt thereof with (i) an ammonia source in the presence of a condensing agent, or (ii) an activating reagent to produce a resultant intermediate, and reacting said resultant intermediate with an ammonia source for conversion of said intermediate into an optically active amide derivative represented by formula (VI):

 or a salt thereof, [wherein in said formula (VI), each of R¹, R², and R³ has the same meaning as defined above]; (C1) when R¹ is an amino group, reacting said optically active amide derivative represented by formula (VI) or said salt thereof with a base for conversion of said optically active amide derivative into an optically active succinimide derivative represented by formula (I):

 or a salt thereof, [wherein in said formula (I), R³ has the same meaning as defined above], or (C2) when R¹ is an amino protected with a protective group, reacting said optically active amide derivative represented by formula (VI) or said salt thereof with a base for conversion into an intermediate represented by formula (VII)

 or a salt thereof, [wherein in said formula (VII), R^(1A) is an amino protected with a protective group, and R³ has the same meaning as defined above]; and eliminating said protective group of R^(1A) on said intermediate represented by formula (VII) or salt thereof for conversion of said intermediate into an optically active succinimide derivative represented by formula (I):

 or a salt thereof, [wherein in said formula (I), R³ has the same meaning as defined above]; (D) reacting said optically active succinimide derivative of formula (I) with 2,5-dimethoxytetrahydrofuran with an acid to produce a first product; (E) reacting said first product of step (D) with a trichloroacetylating reagent to produce a second product; (F) reacting said second product of step (E) with 4-bromo-2-fluorobenzylamine to produce said compound A or said salt thereof; and (G) isolating said compound A or said salt thereof.
 2. The process of claim 1, wherein R¹ is benzyloxycarbonylamino, R² is ethyl, and R³ is ethyl.
 3. The process of claim 1, wherein R³ is ethyl.
 4. The process of claim 1, wherein each of R¹ and R^(1A) is benzyloxycarbonylamino.
 5. The process of claim 1, further comprising reacting an aminomalonate derivative represented by formula (II):

[wherein in said formula (II), R¹ and R³ have the same meaning as defined above] with a halogenated acetic acid ester derivative represented by formula (III):

[wherein in said formula (III), R² has the same meaning as defined above; and Y is a halogen] in the presence of a base for conversion into said ester derivative represented by formula (IV):

or said salt thereof of step (A).
 6. The process of claim 5, wherein R¹ is benzyloxycarbonylamino, R² is ethyl, and R³ is ethyl.
 7. The process of claim 5, wherein R³ is ethyl.
 8. The process of claim 5, wherein each of R¹ and R^(1A) is benzyloxycarbonylamino. 